Focused Ultrasound

PEP Topic

Chronic Pain

Description

Focused ultrasound is a procedure in which sonic ultrasound waves are aimed at targeted areas. This approach was examined in patients with bone metastases with magnetic resonance imaging guidance to target sound waves at metastatic lesions. This was studied for its effect on pain from bone metastases.

Study Purpose:

To evaluate the safety and effectiveness of magnetic resonance–guided focused ultrasound palliative treatment of bone metastases in patients with painful metastatic bone lesions for which other treatment was either not effective or not feasible

Intervention Characteristics/Basic Study Process:

The procedure was done with patients in the magnetic resonance imaging (MRI) scanner under conscious sedation and analgesia with 5–10 mg midazolam and 2–40 mg IV morphine. The dosage was determined by the patients’ previous levels of opioid treatment. Pretreatment MRI and computed tomography (CT) scans were used to identify the treatment region. Each patient was positioned on a table over a water bath containing the ultrasound transducer so that the targeted lesions were positioned over the water bath. At the beginning of the procedure, low-power sonications were done to ensure targeting accuracy, and then treatment at therapeutic power levels was done. Proton resonance frequency shift in water temperature was used to monitor accuracy of the treatment location. At the end of the procedure, contrast-enhanced MRI was used to ensure that ablation was confined to the target tissue and that there was no significant damage to surrounding tissue. Patients had follow-up at three days, two weeks, one month, and three months after treatment. When possible, follow-up was also done at six months. The three-month visit included MR scan and CT imaging. Treatment response was categorized according to criteria of the International Bone Metastases Working Party guidelines on palliative radiotherapy endpoints (partial response was a two-point drop in visual analog scale score (VAS) with no increase in pain medication, or a drop of 25% in pain medication without increase in the pain score).

Sample Characteristics:

The study reported on 31 patients.

Mean patient age was 61 years (range = 40–85 years).

The sample was 51.6% female and 48.4% male.

Breast cancer was the most common tumor type, all patients had bone pain with bone metastases, and 67.7% had prior radiation to the treatment site.

Setting:

Multisite

Setting not specified

Israel, Germany, and Canada

Phase of Care and Clinical Applications:

Patients were receiving end-of-life and palliative care.

The study has clinical applicability for late effects and survivorship.

Study Design:

The study was a prospective, uncontrolled trial.

Measurement Instruments/Methods:

VAS for pain level

Results:

Thirty-six treatments were done, targeting 32 lesions. Average length of treatment was 66 minutes (range = 22–162 minutes). Average sonication energy was 1,135 joules (range = 440–1890 J). No device-related adverse events were reported. Twenty-five patients reached the three-month follow-up time point. In these evaluable patients, mean VAS score before treatment was 5.9; at three days after treatment, mean score was 3.8; and at three months, mean score was 1.8 (p < 0.003). At three months, 72% of patients had a significant reduction in pain (> 2 points), and 50% of patients had no pain. Overall, 36% had complete response and 36% had partial response as defined by the criteria used.

Conclusions:

Limitations:

The study had a small sample, with less than 100 participants.

The study lacked a comparison or control group or blinding.

The authors noted that, in some cases, pain assessment at very specific bone sites was not possible, and this may have contributed to the apparent rate of treatment failures. There were also difficulties in positioning the patient over the water bath, depending on the location of the bone lesion.

Nursing Implications:

This procedure has promise for control of pain from bone metastases in patients who have not responded to other treatment, and, with further research, may have the potential for broader application. Further well-designed research comparing outcomes with this procedure versus that of other current approaches is warranted. Additional research to identify predictors of positive outcomes and those patients for whom this is most likely to be effective and practical according to lesion location would be useful.